The present day continental masses of Australasia, Antarctica, South Africa, Madagascar, India and South America were once a great, single continent that geologists call Gondwanaland or Gondwana.  Evidence of the Gondwanaland connection is still seen in some of the living flora and fauna of those land masses.  For example, marsupials are found in Australia and South America, and plants of the Proteaceae are found in Africa, India, S. E. Asia, Australia and South and Central America but not in Northern America, Europe, North Africa and Asia.  Fossil records show the connection of the Gondwana land masses to a very strong degree.  Some of our fishes, such as the Australian Arowanas or Bonytongues (Scleropages  jardinii and S. leichardti) also show a Gondwana connection.  The Bonytongue family also includes S. formosus (the Asian Dragonfish), Osteoglossum bicirrhosum (the Sth American, Silver Bonytongue), Osteoglossum ferreirai (the Sth American  Black Bonytongue), and the African species, Heteriotis niloticus.

Interestingly, cichlids are found in all of the Gondwana connected lands except for Australia.  Rainbow Fish are found in Australia, New Guinea and parts of S. E. Asia but not in the rest of Gondwana connected lands.

By the Eocene Epoch (55-38 million years ago, during the Tertiary Period), Gondwana had almost split apart, except for parts of old Gondwana such as Australia, Antarctica and South America that remained joined in the south. The Antarctic portion of Gondwana lay at the South Pole but it was free of ice and snow because the global climate was warmer.  A forested corridor linked Australia and South America.
Distribution of land masses during the early Eocene Epoch.

Why do the other Gondwana connected lands have cichlids and Australia does not?

A simple answer is that Australia's freshwater fishes became separated from the rest of Gondwanaland before the cichlids developed in the rest of what was formerly one continent.  The Rainbowfish developed within Australasia after the land masses separated.  That makes the presence of Rainbow Fish and the absence of cichlids a uniquely Australian feature.  That development probably began during the Eocene Epoch.  During that time, Australia was close to Antarctica and the cichlid homelands were warmer places that developed new forests and new animal species that did not develop in Australia and Antarctica.

Fossil Sites in Australia

Australian Biodiversity

 South Australian Dept Environment & Heritage

Watershed Rainbowfish Page

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